City streets and highways utilize gutters and storm drains to remove runoff water so that such routes are maintained in a good driving condition. The drain water collected in the storm sewers is generally carried by underground drainage systems to water shed areas, such as creeks, lakes, rivers, etc. The drainage water carries with it all objects that float as well as objects that are forcefully carried by the currents of the drainage water.
The debris carried by runoff or drainage water into the drainage system is either carried downstream by the water or, if large enough, becomes obstructed in irregularities of the drainage system. For example, the street runoff water that is carried along a curb and into a storm drain, and particularly through a collection box that is constructed below the street level, often lodges therein and forms obstructions for other debris. Larger objects that first become obstructed in the system collect other smaller objects that cannot pass therethrough, and the smaller objects then obstruct yet other smaller objects, and so on until the system becomes completely clogged. If the flow of drain waiter through any part or portion of the drainage system becomes obstructed, the flow rate is reduced, thereby placing additional constraints on other parts of the drainage system. If the blockage or obstruction of the drainage system is not eventually alleviated, flooding and unsafe conditions can result. Cities and highway departments employ maintenance crews for cleaning out and maintaining the storm drain systems in proper operating conditions. It can be appreciated that substantial revenue is required for this purpose alone.
Governmental regulations have recently placed additional constraints on the capability of storm drains, and the like, for carrying silt, sediment and other small-sized earth material. For example, regulations now require that in areas of new construction no silt or sediment particles can be passed through a storm drain and into the downstream rivers or tributaries. These regulations place severe constraints on municipalities in the consideration of areas not yet completely developed, as well as new areas yet to be developed. It is further believed that these constraints will eventually be applied to exiting drainage systems.
Various filter systems have been proposed for use in storm drain systems. In U.S. Pat. No. 122,209 by Ashman et al., an iron grate is installed in a catch basin for removing sticks and other large-sized articles. When the grate becomes filled with objects, the water flows through a peripheral grate area and through the catch basin to the outlet. As can be appreciated, because of the large spacing between the bars of the iron grate, such a system is not effective to remove small-sized particles such as silt.
In U.S. Pat. No. 5,133,619 by Murfae et al., a water filtration system is connected in series with a conventional storm drain system. The filtration system includes a filter basin with a charcoal filter, and a filter basket insertable into the basin. The basket is filled with sand or other fine material. When the filter basket becomes full, a hinged door automatically closes and the drainage water is diverted and proceeds down the gutter to the conventional storm drain inlet where it is carried therethrough to the underground system. The water filtration system of the noted patent can be utilized only in new construction areas as it is not retrofittable into a conventional storm drain system without substantial cost. Such a drain system does not efficiently utilize space, as it is installed upstream from a conventional storm drain system. Also, costly motorized fork lift equipment is required to remove the filter basket and the collected debris and recharge it with a new filter material.
From the foregoing, it can be seen that a need exists for a storm drain filter that can be disassembled and inserted through a curb drain inlet, and easily and quickly installed in the collection box of a conventional storm drain. Another need exists for a storm drain filter that can be easily cleaned without requiring heavy equipment or substantial time. Another need exists for a large-area filter that can remove very small particles such as silt, but yet achieve a high flow rate to accommodate a substantial volume of drainage water. These and other needs are fulfilled by the storm drain filter of the invention as described in more detail below.